Traditionally, methods of applying a waterproofing sheet on a substrate of exterior walls, or around openings such as windows, doors, or the like have been adopted, to protect a building from rainwater, or humidity in the air.
Common waterproofing sheets have both waterproofing property and moisture vapor proofness. Thus, it is impossible to drain moisture, which has been gathered on a substrate, through the sheet. This can be an issue of concern because the gathered moisture can cause corrosion of wood materials or steel frames, which may promote aging of buildings. The gathered moisture can also promote growth of mold or mildew, which may cause indoor air quality issues. As a result, residents may impair their health.
In order to overcome the issue, waterproofing sheets having both waterproofing property and moisture permeability have been developed. One typical example of such moisture-permeable waterproofing sheets is flash-spun nonwoven fabrics. Patent Document 1, for example, discloses a flash-spun nonwoven fabric. Patent Document 2 discloses a method for producing a flash-spun nonwoven fabric. The nonwoven fabric thus obtained has an appropriate pore size. It blocks water, but allows air and water vapor to pass therethrough. A known example of the nonwoven fabric is Tyvek (trademark; produced by DuPont) obtained by thermo-compressing a three-dimensionally-meshed fiber of high-density polyethylene. Such a moisture-permeable waterproofing sheet can prevent external water from infiltrating through the sheet, but can drain gathered moisture as water vapor; thereby, the above issue is to be solved.
However, the openings such as windows or doors is not flat, it is difficult to form a waterproofing layer only with a waterproofing sheet, and therefore the opening is often finished with a waterproofing tape with a pressure sensitive adhesive layer provided thereon. In this case, since the pressure sensitive adhesive layer is made of rubber or asphalt materials, the moisture permeability of the entire tape decreases, and the same problem as that of a common waterproofing sheet can occur.
On laminating the moisture-permeable waterproofing sheet on substrates of exterior walls, overlapped portions of two moisture-permeable waterproofing sheets are often fixed with nails, or pressure sensitive adhesive tapes. As a result, moisture may permeate from nail holes, or gaps of pressure sensitive adhesive tapes over a long period of time.
For overcoming the problem as to waterproofing around an opening or on a substrate of an exterior wall, a liquid-applied waterproofing material having moisture permeability has been developed (see Patent Document 3). In this case, a waterproofing material layer is continuously formed. As a result, the number of gaps formed by a waterproofing tape with a pressure sensitive adhesive layer provided thereon, or a nail remarkably decreases. This solves the problem of aging of a building, and health impairment, and also allows energy saving because of reduction in leakage of the internal air.
However, a composition used in the liquid-applied waterproofing material disclosed in Patent Document 3, etc. contains a latex polymer (aqueous emulsion). Such a composition requires a long period of time to form a continuous layer if it is coated in a condition at a low temperature, or a high humidity. Thus, it is difficult to apply the composition in winter. Moreover, since the coating of the latex polymer is poor in elasticity, it is not able to resist a prolonged strain of a substrate. Thus, cracks, breaks, etc. may occur in or on the coating, and waterproofing property may be deteriorated.
On the other hand, it has been known that an organic polymer that contains at least one reactive silicon group in a molecule can give a rubbery cured product. Such an organic polymer can crosslink even at a room temperature by forming siloxane bond through hydrolysis of the reactive silicon group under an existence of moisture in the air.
Patent Document 4, etc. discloses a reactive silicon group-containing organic polymer whose main chain is a polyoxyalkylene polymer among these reactive silicon group-containing organic polymers. Such a polymer has been already produced in a commercial scale, and widely used as sealing materials, adhesives, etc.
The polyoxyalkylene polymer having a reactive silicon group has a comparatively low viscosity. Thus, a nonaqueous liquid-applied waterproofing material, which is solvent-free, or contains a small amount of solvent and has sufficient workability can be designed. Further, a polyoxyalkylene polymer having a reactive silicon group can be practically cured even at a low temperature. Thus, it can be used in winter. Further, the polyoxyalkylene polymer having a reactive silicon group produces a rubbery cured product with favorable elasticity. Thus, such a rubbery cured product is expected to have sufficient resistance to strain from the substrate.
However, the liquid-applied waterproofing material, which is made of a known curable composition that contains this polymer, shows insufficient moisture permeability, although the material provides waterproofing property almost equivalent to that of the waterproofing sheet. Accordingly, the aforementioned problem has not been completely solved up to now. The present invention has its object to improve moisture permeability of the liquid-applied waterproofing material while maintaining waterproofing property.
By the way, a polyoxyalkylene plasticizer is effective to achieve the object of the present invention, and general polyoxyalkylene plasticizers have been used in some cases. There are some previous reports on curable compositions that contain polyoxyalkylene plasticizers. Patent Document 5 discloses a curable composition that contains a polyoxyalkylene plasticizer. The curable composition disclosed in Patent Document 5 shows a favorable viscosity, and causes no sedimentation-separation, or slump. Patent Document 6 discloses a technology of improving coatability of an alkyd paint composition on the surface of a cured product by a polyoxyalkylene plasticizer. Patent Document 7 discloses a technology of improving storage stability by a polyoxyalkylene plasticizer.